Phase-converting system.



R. E. HELLMUND. PHASE CONVERTING SYSTEM.

APPLICATION FILED JAN. 23, I915.

Patented Mar. 4,1919.

R O T N E V m WITNESSES d H u m u 8 H E U. d u B AiToRNEY UNITED STATESPATENT OFFICE.

BUDOLI' E. HELLMUND, OF YITTSBUBGH, PENNSYLVANIA, ASSIGNOR '10 WESTING-HOUSE ELECTRIC ANiD MANUFACTURING COMPANY, CO RPORATION OF PENNSYL- VANIA.

PHASE-CONVERTING SYSTEM.

Specification of Letters Patent.

' Patented Mar. 4., 1919.

Application filed January 2a, 1915. Serial No. 3,917.

To all whom it may concern:

Be it known that I, RUDoLF E. HELL- MUND, a subject of the GermanEmpire, and a resident of Pittsburgh, in the count of Allegheny andState 0 Pennsylvania, ave invented a new and useful Improvement inPhase-Converting Systems, of which the following is a specification.

My invention relates to systems of alter,- nating-current distributionand to control systems for alternating-current motors, and it hasspecial reference to the control of railway polyphase induction motorsthat are adapted to receive energy from a singlephasesource ofdistribution. v

()ne of the objects of my invention is to provide a distributing andcontrol system of the above indicated class which shall embody analternating-current dynamo-electric machine of the commutator type thatis arranged and connected in such manner as to serve as a phaseconverter b 1 means of which the single-phase energy 0 the source isconverted into polyphase energy for the operation of the polyphaseinduction motor.

It is another object of my invention to utilize an alternating-currentcommutator converter for the purpose specified and to make simple andeffective provisions for ad justing the circuit connections of theconverter, whereby compensations for phase distortions and voltagereductions of the converter voltage may be readily accomplished.

In another aspect, it is an object of my invention toprovide analternating-current commutator machine havina plurality of distinct mainexciting fielf windings, one of which is a shunt winding and isenergized from a constant source and the other of which is a seriesWinding and is influenced in proportion to the main current whichtraverses it, whereby an alternating-current commutator machine havingsubstantially compound electrical characteristics is obtained. Moreover,I propose to employ a dynamo-electric machine of this type as a phaseconverter in the manner already referred to and to thus secure anautomatic compensation of the converter phase distortion in accordancewith variations in the load conditions. i v

'In a co-pending application, Serial No. 808714, filed December 26,1913, by Benjamin G. Lamme and assigned to the Westinghouse Electric &Manufacturing Compan a system of distribution and control is disc osedwhich is adapted to supply polyphase energy to the drivin motors from asingle-phase source throug the agency of a phase converter of theinduction type. Provisions are also made for making adj ust- -ments ofthe converter connections for efof automatic regulation by means of acompound type of alternating-current commutator mac me, I find itnecessary to place the respective shunt and series windings thereof uponindependent polar projections in order to obviate mutua inductionbetween -the windings which would otherwise render the series windinguseless.

' These and other objects are sought by the peculiar arrangement andcircuit connections of my invention, and, although I shall illustrate itin connection with a few simple arrangements of circuits, it should beunderstood that it is not so restricted, but is capable of wide andvarious applications.

In the accompanying drawing, Figure 1. is a diagrammatic view of asystem of distribution and control embodying my invention; Fig. 2 is a"ector diagram showing the relationship of certain of the voltages ofthe system; Figs. 3, 4 and 5 are digrammatic views of modifications ofmy invention; and Figs. '6 and 7 are diagrammaticviews of the circuitconnections of two forms of com-. pound commutator machines such as areadapted for use in the system shown in eye:

tem 5.

1. Referring to Fig. 1, a supply conductor 1, such as a trolleyconductor of a railway system, delivers single-phase energy to a primarywinding 2 of a transformer 3 which 1s provided with a secondary winding4 having a plurality of sets of taps 5 and 6 to which connections may bemade by means of adjustable switching devices 7 and 8.

A phase converter 10 of the single-phase commutator type embodying anarmature 11, a main exciting winding 12 and an auxiliary compensatingwinding 13, 1s connected to the transformer secondary winding 4 andserves, in conjunction therewith, to supply polyphase energy to primarywindings 14, 15 and 16 of a three-phase induction motor 17 havingsecondary windings 1.8, 19 and 20 that are connected to an adjustableresistance device 21 that may conveniently take the form of a liquidrheostat.

The commutator phase converter 10 may be of a construction similar tothat of an ordinary single-phase commutator motor,

' across a having its main exciting winding 12 disposed in substantialquadrature relat on with its secondary oompensatlng winding 13. Theexciting winding 12 is connecte ortion of the transformer secondary wining 4 by means of a switching'device 7. The excitation thereof,therefore, is in phase with the source of energy and may be varied, asdesired, by shiftin the connections'to the various taps 5. ture 11embodies suitable windings (not shown) which are connected to acommutator :24 which is provided with a set of brushes 25 in the usualmanner. One of the brushes 25 is connected to substantially themid pointof the transformer secondary winding 4'by means of the switching device8 and said connection may be shifted to the one or the other sidethereof by suitable adjustments of said device. The compensating winding13 is connectedin series with the armature 11, and the machine is sodesigned that the armature is adapted to deliver a quadrature voltage ofsubstantially 86.6% of that of the transformer winding 4. The machine 12may be driven by any suitable means, such as a car-axle 22, in a mannersimilar to that disclosed, for example, in -U.'S. Patent No. 977,784,issued to the Westinghouse Electric & Manufacturing Compan on Dec. 6,1910, on an application filed by illiam Cooper.

It is evident, therefore-that the voltage of thearmature 11 may becombined with that of the transformer winding 4 in such manner as toproduce balanced three-phase voltages by' connecting brush 25 of thearmature 11 to the mid point tap 6. The connections just referred to arethus similarto those of the well-known Scott or T system and will bereadily understood. I

A consideration of Fig. 2-will show .the relationship of theelectromotive forces above mentioned, E, being the electromotive forceof the transformer winding 4' and in phase with the source of energy,and E being the electromotive force of the armature 11 of the phaseconverter 10 and which thus permitting the motor 17 to be .he arma-'.result with respect to the is at 90 from the voltage E With thisrelationshi and the voltage E e'ual to substantial y 86.6% of thevoltage it is clear that the electromotive forces E x and E are equaland disposed at 120 rom each other. Thus, three-phase energy of balancedelectromotive forces is produced from a single-phase source.

Assuming the phase converter to be inoperation and the connections to beas shown in Fig. l, the operation of the system is as follows:Electrolyte is first admitted into the rheostat 21, whereby the motorsecondary resistance is correspondingly reduced,

a'dually brou ht u to s eed in accor ance with well l nown principles.

Under light or no-load conditions upon the motor'17, the balancedvoltage relatlonship is maintained. However, as the motor load isincreased, there is a tendency for the electromotive force delivered bythe armature 11 of the converter to be displaced somewhat in phaseposition and also to be reduced in amount by reason of the impedance ofthe apparatus. Any phase displacement, of course, disturbs the initialbalanced condition of thethree-phase voltages and is thereforeundesirable. It is, therefore, necessary to provide means forcompensating for any voltage reduction and phase displacement duringvarying load conditions andthis is accomplished by means of theswitching devices 7 and 8.

Reference may a ain 'be had to Fi 2, and, for purposes 0 explanation, itwi 1 be assumed that, by reason of load conditions, the point P of thediagram is moved to P, which position depends upon the phase distortionand voltage reduction of the electromotive force of the armature 11 ofthe converter.

'The phase distortion may be compensated for by causing the switchingdevice 8 to connect} one terminal of the armature to the lproperintermediate tap 6 at one side of]; amid-point of the winding 4. ThisadJustment of connections effects the desired hase distortion duringmotor operation. ff, however, the motor 17 should 'be driven as agenerator for delivering energy back to the line, the adJuStmcnt ofconnections must be made to the opposite side of the mid-point.

Having compensated for the phase dis placement, thus bringing the pointP to a position P it is further necessary to raise the voltage'of thearmature 11 to its initial value to secure balanced electromotiveforces. This voltage adjustment may be effected by increasing theexcitation of the main exciting windin 12 of the converter 10 throughthe switchlng device 7, and, dur ing this operation, it is necessary tohandle comparatively small exciting currents only.

erator for regeneration to the line, the point,

' P may be assumed to occup a position? under load conditions when t ephase distortion and voltage variation is uncompensated. Normal balancedconditions of regeneratlon may, of course, be secured in a manneranalogous to that already explained, and no description thereof isdeemed necessary..

Referring now to Fig. 3, the modification shown difiers from thatalready described chiefly in that the armature 11 of the con-' verter 10is short circuited uponitself, and

the auxiliary compensating field winding 13,

instead of being connected in series circuit with the armature 11, isindependently con nected to substantially the midpoint of thetransformer winding 4 by means of the switching device '8. Although thearrangement of circuits of this system is modified in some respects, thegeneral operation thereof is essentially the same as that of the systemof Fig. 1, and similar adjustments. and compensations ma be effected.

In Fig. 4, I have illustrated a modified s stem that is adapted todeliver energy to the primary windings 28 and 29 of a twophase'inductionmotor 17%. The converter 10 has it's armature 11 short-circuited uponitself,'while its exciting winding 12 1s connected across a portion ofthe transformer winding 4, as already explained. The auxiliarycompensating winding 13, however, isconnected in series circult with themotor primary winding 29 and with a secondary winding 30 of an auxiliarytransformer 31 having its primary windin across a portion of the maintransformer winding 4. by means of a switching device:

33. The motor primarj; winding 28 is connected directly across t emaintransformer winding 4, and the converter 10 is so de-..

signed that the generated quadrature voltage of the winding 13 is equalto that of the source, whereby balanced voltages are sup- 'the circuitof the converter winding 13 and motor winding 29, a voltage which is inphase with the source of energy and effects a resultant shifting of thephase position of the voltage delivered to the motor, Moreover, thisadditional out-of-phase voltage varies in accordance with variations inload,

-to a certain extent, dependent upon the regulation of the transformers3 and 31,

as will be understood, whereby partially 32 connected automaticregulation of the phase distortion is obtained. Further and more exactadj ustments may be effected by suitable manipulation of the switchingdevice 33.

Obviously, similar automatic re ulation may be accomplished by the use 0a suitvide polyphase' energy for three-phase apparatus through theagency of a commutator type phase converter having windings and circuitconnections that are peculiarly adapted to effect automatic regulationof the phase position of the converter voltage in accordance withvariationsin the! load upon-the driving motor. I

In this case, the armature 11 has oneof its terminals connected to themid-point of an auto-transformer winding 4 and the auxiliarycompensating field winding 13 is shortclrcuited upon itself. The mainexciting field winding comprises two parts, a field winding 12 whichcorresponds, in all res ects, to the winding 12 hereinbefore descrlbedand which constitutes a shunt winding that receives a constantexcitation from a portion of the transformer-winding 4, and a winding12' which constitutes a series winding and is connected in seriescircuit between the supply conductor 1 and the transformer winding 4"and, hence, is variably excited in accordance with the load.

In order to secure the benefits of this-compounding, or combined seriesand shunt eld winding, it is necessary to prevent any mutual inductionbetween them, and, therefore, the field magnet structure is arranged inthe manner shown in Fig. 6. The field ma net structure embodies aplurality of split main polar projections 37 and 38 and intermediateauxiliary .polar projections 39 sections which are connected in seriesand respectively disposed upon the polar members 37 and 38", while theshunt field winding 12 is similarly divided into sections which aredisposed upon the polar members 37 and 38 and connected inseries-circuit relation. The compensating winding 13 is associated withthe'auxiliary polar projections 39 and 40, being also divlded into twoparts that are short-circuited, the one upon the other.

An alternating-current commutator machine having compoundcharacteristics is thus provided which isanalogous, so far as itsoperation is concerned, to the well-known as a generator, in many othercla'ses of-sys-. g tems.

In Fig. 7 the character referred to which embodies a four-pole fieldmagnet arrangement and a two-circuit series armature. The field magnetstructure 36 comprises a plurality'of main polar projections 45, 46, 4:7and 48, and

the shunt winding 12 has its respective sections associated with thepolar projections 45 and 46 while the projections 47 and 48 carr thesections of the variable series win 'ng 12" v Other modifications in thestructural details and circuit connections of my improved form ofcommutator phase converter an also of the arrangement of parts, circuitsand mode of operation of the system of distribution and control, as a-.whole, may be effected without departing from the spirit and scope ofmy invention, and I desire that only such limitations shall be imposed.as are indlcated in the appended claims.

I claim as my invention:

1. The combination with a source of single-phase energy, andatransformer receiving energy therefrom, of a single-phase commutatordynamo-electric machine comp-rising a main shunt field windingconnectcdacross a portion of said transformer, a series field winding connectedin series circuit with said transformer, driving means therefor, and anarmature connected in an independent circuit to said transformer.

2. The combination with a source of single-phase energy, and atransformer receiving energy therefrom, of a single-phase commutatordynamo-electric machine comprising an armature having one terminalconnected to an intermediate point in said transformer, a main fieldwinding excited in is shown a modified machine of the load upon saidphase with said transformer across a portion thereof other means forvarying the excitation of said machine in accordance with loadconditions, driving means therefor, and' a polyphase electric motorreceiving energy from said transformer and said, dyna-moelectricmachine. 3

3. The combination with a single-phase source of energy, a transformerconnected thereto and a polyphase electric motor, of a sin le-phasecommutator converter provided wit driving means for supplementing saidsingle-phase energy to supply polyphase'en-.

ergy for said motor and comprlsing a plurality of exciting fieldwindings respectively connected across a portion of said transformer andin series therewith, whereby the bass distortion of said converter,under oad conditions, is automatically corrected. 4:. The combinationwith a single-phase source of energy, a transformer connected theretoand a polyphase electric motor, of a I sin le-ph'ase commutatorconverter provided wit driving means for supplementing said single-phaseenergy to supply polyphase energy for said motor and comprising an armadture and a two-part-exciting field winding,

one part being constantly excited from said transformer and the otherpart being excited in accordance with changes in load upon said electricmotor.

, 5'. The combination with a source of single phase energy, andpolyphase electric means receiving energy therefrom, of means interposedbetween said source andsaid polyphase means for supplying single-phaseener of displaced phase and embodying a sing e phase commutatordynamoelectric machine having a substantially constantly excited fieldwinding and a-nother'field winding excited in accordance with variationsof lyphase; means, whereby compensations or phase distortions in iaidconverting means are automatically ef- In testimony whereof, I havehereunto subscribed my name this 21st day of Jan RUDOLF' E. HELLMUND.

Witnesses: I J. V. DoBsoN,

B. B; HINES.

